Lewis on Idiosyncratic Analysis
Apropos conceptual differences, Lewis didn't seem to care much about whether his analyses exactly matched other people's semantic intuitions:
In "Veridical Halluzination and Prosthetic Vision", he claims that prosthetic vision is properly called "seeing". He continues:
If you insist that "strictly speaking", prosthetic vision isn't really seeing, then I'm prepared to concede you this much. Often we do leave semantic questions unsettled when we have no practical need to settle them. Perhaps this is such a case, and you are resolving a genuine indeterminacy in the way you prefer. But if you are within your rights, so, I insist, am I. I do not really think my favoured usage is at all idiosyncratic. But it scarcely matters: I would like to understand it whether it is idiosyncratic or not. (p.280 in Papers II)
Another example: In Convention, he suggests that a regularity to dress in a particular way doesn't count as conventional if many people conforming to the regularity want others not to conform (so that they can poke fun at them). Realizing that this classification isn't obvious he notes:
If the reader disagrees, I can only remind him that I did not undertake to analyze anyone's concept of convention but mine. (p.47)
He speaks of reminding the reader because he had already mentioned in the introduction that there might be no clear common concept of convention. But, he adds, "what I call convention is an important phenomenon under any name" (p.3).